Amygdala: The Gateway to Fear
Written by Laasya Alampali
Understanding the Amygdala
The amygdala is a small, almond-shaped structure inside the brain. It is part of a larger system in the brain, known as the limbic system. The amygdala and limbic system are crucial for survival as these components are responsible for detecting danger and triggering the body’s fear response. The amygdala processes visual and auditory stimuli from various areas of the brain to learn what is and is not dangerous for the human body. If a situation surrounding the same input appears again, the amygdala accordingly generates an appropriate emotional response.
This element of the brain is located in the temporal lobe. The amygdala neighbors other structures that carry information regarding the five senses to and from the brain. It has nerve pathways to the thalamus – the body’s relay station-, the hippocampus, and other neurological structures that record internal and external activity of the body and its surroundings.
Studies Concerning the Amygdala and Fear
Brain imaging studies such as PET (Positron Emission Topography) and fMRI (Functional Magnetic Resonance Imaging) are used to show when and how the amygdala is activated and what scenarios prompt its activity. A study was conducted using these technologies with 55 participants. While being exposed to fearful stimuli, the amygdala of 25 participants “lit up,” displaying activity. This study, although simple, clearly proves that the amygdala is directly involved in regulating fear responses.
Another study regarding the amygdala was performed on rodents to demonstrate the negative effects of lesions on the amygdala in fear regulations. A lesion is “a region of an organ or tissue which has suffered damage through injury or disease such as a wound, ulcer, abscess or tumor” (Oxford Dictionary). In this investigation, rats with lesions to their amygdala were exposed to common fear triggers such as cats or cat hair. Typically, these factors should send a message to the rodent’s brain, immediately causing a freezing and panicking action. However, these lesions caused a visible delay in the external fear output, which could be crucial to a rat’s survival in non-controlled environments.
Anxiety Disorders and the Amygdala
An anxiety disorder is a type of mental health condition that causes people to respond to certain scenarios with fear or dread. Symptoms include restlessness, shortness of breath, obsessive thoughts, etc. Disruptions in the amygdala can aggravate fear and cause extreme reactions to certain scenarios in people who suffer from anxiety disorders. Additionally, various “anxiety cues” are present in brains with anxiety disorders. Since the amygdala plays a major role in one’s fear, it also plays a major role in one’s levels of stress. Highly imbalanced levels of stress are also common indicators of anxiety disorders caused by an abnormal amygdala.
References
AbuHasan, Q., Reddy, V., & Siddiqui, W. (2023, July 17). Neuroanatomy, amygdala. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK537102/#:~:text=Structure%20and%20Function&text=%5B1%5D%20The%20amygdala%20also%20has,dorsomedial%20nucleus%20 of%20the%20thalamus.
Limbic System: Amygdala (Section 4, Chapter 6) Neuroscience Online: An electronic textbook for the neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston. (n.d.). https://nba.uth.tmc.edu/neuroscience/m/s4/chapter06.html
Professional, C. C. M. (2024a, May 1). Amygdala. Cleveland Clinic. https://my.clevelandclinic.org/health/body/24894-amygdala
Ressler, K. J. (2010). Amygdala activity, fear, and anxiety: Modulation by stress. Biological Psychiatry, 67(12), 1117–1119. https://doi.org/10.1016/j.biopsych.2010.04.027
Written by Laasya Alampali from MEDILOQUY